Scale inhibitors are used, for example, in offshore oil production for stimulation of the oil wells, for controlling and/or preventing scale depositions. A scale inhibitor may be injected continuously into an oil well, or it may be periodically injected if a so-called squeeze treatment is employed. In the squeeze treatment a scale inhibitor pulse is injected into the oil well and the scale inhibitor leaches back into the produced fluids. The concentration of the scale inhibitor in the produced fluids should be sufficiently high in order to avoid scale formation or precipitation. The concentration of scale inhibitor normally decreases exponentially after the initial injection, and when the concentration has fallen below a predetermined value the squeeze treatment of the oil well is repeated. Consequently, it is important to obtain reliable knowledge about the concentration of the scale inhibitor in the produced fluids for securing well-timed squeezing treatment. If the squeezing treatment is performed too late, harmful scales may be formed and disturb the production process.
Nowadays different analytical techniques are used for determining the scale inhibitor concentration in the produced fluids. Examples of used techniques are inductively coupled plasma (IPC), high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS). However, there is a continuous need for new, accurate and simple analysis methods.
Furthermore, in many oilfields a number of oil wells are squeezed at the same time. The produced fluids are a mixture of fluids from all the oil wells, and comprise scale inhibitor traces from each well. If different scale inhibitors are injected into each of the oil wells, it would be advantageous if the concentration of the different scale inhibitors could be determined separately. This would enable the correct individual squeeze treatment cycle for each oil well, separately from the other oil wells.